1. Field of the Invention
The present invention relates to a method of making highly reflective metal strips, and in particular to a method of making reflective aluminum trim for use in automobiles, trucks, boats and a variety of household and industrial appliances.
2. Background Information
Decorative trim is widely used in automobiles, trucks, boats and a variety of household and industrial appliances. Such decorative trim has conventionally been made from stainless steel due to its high reflectance, corrosion resistance and durability. However, the relatively high cost of stainless steel has prompted its replacement with aluminum trim. In addition to cost savings, the use of aluminum trim instead of stainless steel can result in weight savings for automobiles, trucks and the like.
U.S. Pat. No. 5,290,424, which is incorporated by reference herein, discloses a method of making shaped reflective aluminum strip protected by an anodic oxide coating and a light-permeable fluoropolymer coating. The method involves the steps of bright rolling aluminum alloy sheet, anodizing to prepare the surface of the sheet for subsequent coating, applying a fluoropolymer protective coating to the sheet, slitting the coated sheet to form strips, and roll forming the coated strips. After roll forming, adhesive is applied to the coated strips and then cured. A co-extrusion process is then used to apply a thermoplastic such as vinyl to the coated aluminum strips. While the disclosed method produces highly reflective aluminum trim with good durability, it is relatively expensive due to the large number of manufacturing steps involved. In addition, the fluoropolymer protective coating must be applied to the entire surface of the aluminum sheet instead of selected portions of the formed strips, which adds to the cost of the final product.
U.S. Pat. No. 5,478,414, which is incorporated by reference herein, discloses a method of making shaped reflective aluminum strip similar to the process disclosed in U.S. Pat. No. 5,290,424, except the surface cleaning and protective coating steps are combined into one operation. In this process, the aluminum alloy sheet is cleaned, chrome conversion coated, and roll coated with a fluoropolymer protective coating, all in one operation. The coated aluminum sheet is then slit to width and roll formed in a similar manner as disclosed in U.S. Pat. No. 5,290,424. A corona discharge is used to treat the coated strip prior to application of the adhesive.
U.S. Pat. No. 5,637,404 filed Oct. 18, 1995, which is incorporated by reference herein, discloses a method of making shaped reflective aluminum strip similar to that set forth in U.S. Pat. No. 5,478,414, with the exception that a chrome-free conversion coating is used and corona treatment is not necessary prior to application of the adhesive.
In each of the above-referenced disclosures, the fluoropolymer protective coating is applied to at least one entire side of the aluminum sheet, followed by slitting to width and subsequent roll forming. Since a large portion of the aluminum strip is subsequently covered with vinyl to form the final trim piece, the application of the fluoropolymer protective coating over the entire surface of the aluminum sheet represents an unnecessary expense. In addition, it is difficult to adhere vinyl to the fluoropolymer protective coating. Corona discharge treatments and/or specialized adhesives are thus preferably used to adhere the vinyl to the fluoropolymer coating. Furthermore, since the strips are roll formed after the fluoropolymer protective coating is applied, the protective coating must be able to withstand crazing, debonding and other deleterious effects of the forming operation, which may result in a final coating that has less than optimum hardness.
Despite the above-noted processes, a need still exists for producing low-cost reflective aluminum trim with a minimum number of manufacturing steps. The present invention addresses these needs as well as other deficiencies of the prior art.